Abstract: Objective: To analyze the diagnostic value of cerebrospinal fluid (CSF) laboratory test in patients with neurosyphilis and HIV positive and the application of RPR (rapid plasma reagin test) titer and CD4+ T cell count in neurosyphilis lumbar puncture indication. Methods: One hundred and six patients with syphilis were collected from January 2015 to December 2019 in Beijing You'an Hospital. CSF was collected for CSF white blood cell (CSF-WBC), CSF protein (CSF protein) and CSF TPPA (Treponema pallidum particle assistant), According to the diagnosis of neurosyphilis, the patients were divided into neurosyphilis group and non neurosyphilis group. The results of cerebrospinal fluid test, serum RPR titer and CD4+ T cell count were analyzed. Results: Totally, the data of 106 cases were collected in the study. The incidence of neurosyphilis in 106 patients with syphilis and HIV positive was 33.02%, and the sensitivities of CSF-RPR and CSF-TPPA to the diagnosis of  neurosyphilis in HIV positive syphilis patients were 68.57% and 97.14%, specificities were 92.96% and 49.29%, respectively. ROC (receiver operating characteristic curve) of CSF-WBC and CSF-protein were analyzed (AUC area under). The area under the curve was 0.911 and 0.913, respectively. When CSF-WBC count was 10.5/μL and CSF protein level was 272.15 mg/L, the yoden's index was the highest. The incidence of neurosyphilis in patients with serum RPR≥ 1∶16 was 1.52 times higher than that in patients with serum RPR<1∶16 (OR 1.52, CI 1.14-2.04, P< 0.05). The incidence of neurosyphilis in patients with CD4+ T cell ≤350/μL was 2.37 times higher than that in patients with CD4+ T cell >350/μL (OR 2.37, 95％ CI 1.64-3.41,P<0.05). Conclusion: The incidence of neurosyphilis in syphilis patients with HIV positive is high. CSF-RPR has high diagnostic value for neurosyphilis in syphilis patients with HIV positive. Serum RPR titer more than 1∶16 and CD4+T cells less than 350/μL are risk factors for neurosyphilis in patients with syphilis and HIV positive.

Key words: neurosyphilis, RPR, TPPA, CD4+T cell